Method of manufacturing hollow poppet valves for internal combustion engines



Aug. 9, 1960 G. KUBERA METHOD OF MANUFACTURING HOLLOW POFPET VALVES FORINTERNAL COMBUSTION ENGINES Flled May 27 957 INVENTOR. GER/ 19190 4 1/859 BY #esfiued 2,

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United States Patent METHOD OF MANUFACTURING HOLLOW POP- FOR INTERNALCOMBUSTION Gerhard Kubera, Blumberg, Baden, Germany, assignor to AlfredTeves Maschinenund Armaturenfabrik KG., Frankfurt am Main, Germany FiledMay 27, 1957, Ser. No. 661,647

Claims priority, application Germany June 30, 1956 i 3 Claims. (Cl.29156.7)

The present invention relates to a method of manu' facturing hollowpoppet valves, and is an improvement on the method described in myprevious U.S. Patent No. 2,731,708. In that patent there is described amethod of manufacturing hollow disc valves wherein the unfinished blank,formed with a blind end bore into which is inserted a core portion ofsteel, is subjected to a drawing operation so as to produce a forging.The drawing operation results in the formation of a stem having apredetermined outer diameter and an integrally formed therewith valvehead portion. Following the drawing step, the core is Withdrawn from theblind end bore, or may remain therein when properly shaped, whereupon aforging operation takes place.

Forging dies of high strength alloy substances have been employed in theprocess heretofore. However, these dies have been unable to meet theexacting demands of the process. Their span of usefulness has been veryshort, especially when employed with bores of smaller diameters e.g.under 15 mm. The wear on the outer surfaces of such dies has been soextensive, that the blind end bores have been subject to undesirablevariations.

In addition, since the core portion could not be specially fitted ineach bore, it has been necessary to change the forging dies frequentlyto maintain a better tolerance.

The present invention seeks to overcome the above disadvantages.

According tothe invention, a set of blanks is heated to forgingtemperature and inserted into a die. Next, the cold core pieces whichhave been previously tempered to a predetermined hardness are insertedcentrally in the heated and consequently glowing set of blanks to agiven depth.

The blanks, together with the core pieces therein are subsequentlyprocessed substantially according to the method described in my previousU.S. Patent referred to above.

The process will be further illustrated and described in terms of theaccompanying drawing which is given by way of illustration and not oflimitation, and wherein Fig. 1 indicates an unfinished blank 7 formedwith a blind end bore in which the cold core piece 2, previouslytempered to a predetermined hardness has been inserted.

2,948,052 Patented Aug. 9, 1960 Blank 7 has been pre-heated to a forgingtemperature and is in a glowing state.

Fig. 2 shows the same blank 7 and a core piece 6 therein, resulting froma drop-forging operation. Numeral 8 in that figure indicates a head ofthe core blank in a correspondoing recess of the blank.

Fig. 3 illustrates another form of a blank 9 and a core portion 10.

Fig. 4 illustrates the finished valve with the core piece removed andthe resulting opening closed OE With a cover 11.

The steps of the method according to the invention are as follows:

Into a billet wherein a blind bore has been formed, and which has beenheated to forging temperature, is inserted a cold core piece which hasbeen previously tempered to a predetermined hardness. Next, the blank isdrop-forged so that the top of the blank is expanded to form a cavity inthe valve bonnet for purposes of more effective cooling. The coreremains in the blank while being forged. When the operation iscompleted, the core piece is removed from the blank now formed into avalve body and the valve head is formed in a. known manner.

Finally, the valve is closed with a cover before or after introducing acoolant medium into the cavity in a known manner. Butt or lap weldingmay be advantageously used to attach the cover. Alternatively, the stockof the valve itself may be used to close the cavity.

Having thus described the method of my invention, what I claim as newand desire to secure by U.S. Letters Patent is:

1. The method of manufacturing hollow poppet valves for internalcombustion engines which comprises the steps of piercing a blind hole ina billet, next heating the billet to forging temperature and glowingstate, inserting into the blind hole of the billet a steel core portionwhich has been previously tempered to a given hardness, subjecting saidbillet with the steel core portion therein to a forging operation forforming a valve body, removing the steel core piece from the valve bodythus formed, and finally closing the open end of the valve body.

2. The method according to claim 1, wherein a coolant is introduced intothe valve blank after the removal of the core portion and prior toclosing the opening'in said valve.

3. The method as claimed in claim 1, wherein the valve is additionallyfinished by forging the material at the head thereof.

References Cited in the file of this patent UNITED STATES PATENTS774,242 Gates Nov. 8, 1904 2,170,811 Cornell Aug. 29,1939 2,177,192Scrimgeour Oct. 24, 1939 2,452,628 Bartlett et al. Nov. 2, 19482,452,636 Cunningham et a1 Nov. 2, 1956 2,731,708 Kubera Ian. 24, 1956

